Process for the regeneration of acetylene absorbing liquids



Filed Oct. 7, 1955 J. E. BLUDWORTH El' AL wwwa II Dunk JlLv PROCESS FORTHE REGENERATION OF' ACETYLENE ABSORBING LIQUIDS Nov. 3, 195,9

INVENTORS.

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wel h /w ky www United States Patenti() PROCESS Fon THE REGENERAnoNoFACETY- LENE ABSGRBING LIQUIDSy f f Joseph E. Blndworth, Corpus Christi,and Clyde Leatherwood, Brownsville, Tex., assignors to Delhl- Taylor OilCorporation, Dallas, Tex., a corporation of Delaware Application october7, 195s, seriarNo. 539,252' j 12 claims. -(ci. 1ss,j1'1s)`v Thisinvention relatesto a processl for the regeneration ofv an organicabsorbing. liquid,y and',y more particularly pertains to a process forthe removal of acetylene and its homologues from acetone.VPreviously-1t'V had been the practice to strip acetylene dissolved inace7 tone by means of a gas inert to the acetone absorbent@20 wasremoved, only small amounts of the acetylene'h'omo'- and the gasesdissolved therein. Although the acetylene 2,91 1,067 Patented Nov. 3,1959 quantity of stripping gas. The overhead gaseous discharge from thesecond stripping tower comprising vinert gas and acetylene homologuesand polymers is washed and vented to the atmosphere. The acetone andwater bottoms emerging from the second stripping tower are passed into adistillation tower ,in which the acetone may be distilled from the waterin a state of high purity.

In a modilication'of'the above process, additional l acetoneessentiallyfree of acetylene but containing some methyl acetylene may be mixed withthe bottoms from the lirst acetone stripping tower to effectremoval ofmethyl acetylene Ytherefrom in the second"v stripping' tower. v f

As a second modification of -the'fabove process the acetone-waterbottoms from the second stripping tower may be filtered to remove anyhi'gum'olecular Weight polymers which may have precipitated out duringthe in nature and therefore removable 'only with'ffgreat-r Thisinvention has as an object, therefore, the provision of a continuousprocess for the removal of acetylene and its homologues from an organicabsorbent in which the acetylene homologues are readily removed asgases.

It is a furtherobject of this invention to provide an absorbentregeneration process"in"whch,thelinal absorbent product is ,of highpurity;` i

A further object of this invention is the provision of a solventabsorption process for acetylene in which at least a portion of thesolvent is treated to remove acetylene homologues and polymers prior torecycle to the system.

It is another object of this invention to provide an organic absorbentregeneration process in which the formation of solid acetylene polymersis substantially obviated, thereby facilitating the iinalabsorbent-acetylene polymer separation. l

It is a still further object of this invention to provide an absorbentregeneration process in which only water need be employed as theagent'reducingthe'solubility of the acetylene homologues in theabsorbent, thereby enhancing the overall economic feasibility of theprocess.

Further and additional objects will appear from the followingdescription, the accompanying drawing and the appended claims. f A w Inaccordance with one embodiment of this invention an organic absorbenthaving acetylene and its homologues dissolved therein ispassed into arst stripping tower in countercurrent engaging flow with a stripping gaswhich is inert to the absorbentand the gases Idissolved therein. Thestripping gas removes substantially all of the acetylene but very littleof the acetylene homologues and polymers contained therein; the overheadgaseous discharge is cycled for acetylene recovery. The acetone bottomscontaining acetylenehomologues dissolved therein are miXedKWith watertoV force the normally gaseous acetylene homologues such as methylacetylene and gaseous polymers such as diacetylene to come out ofsolution, as a result of theirreducedsolubility in the diluted acetone.The diluted bottoms from the rst tower are then passed into a secondstripping tower in countercurrent engaging ow with a second eluentemerging from vthe column 10 through line y16,

contains primarily acetylene and inert gases which are' acetone dilutionstep, prior to passing the bottomsl into the distillation zone. f

For a more complete understanding of this invention,`

reference will now be made to the accompanying drawing which is aowpl'an of-the solvent regeneration process.

Referring now to the flow sheet, a gaseous ystream con taining acetyleneand itsv homologues-is shown entering a packed tower orcolumn 10 bymeans of a linen 12,.

The gaseous stream may beproduced in accordance with any of theprocesses for the production of acetylene by the partial combustion ofhydrocarbons, and maybe produced in accordance-with the teaching ofcopending Joseph C. Bludworth' application Serial No. 224,540,

led May 4, *1951, now Patent No. 2,785,213, issued March 12, 1957. Sucha gas suitably contains acetylene," hydrogen, carbon monoxide, and smallamounts of other'V gasesincluding the polymers and homologues ofacetylene. Prior to entering the contacting column 10, the gaseousstream containing the gases of reaction from an acetylene-producingprocess are compressed to approximately 200 pounds pressure per squareinch. "Ihe gases entering Vthe bottom of the column 10 countercurrently,contact a downwardly llowing stream of acetone or other" suitableorganic absorbent entering the top of theA contacting column 10 at apoint adjacent the -ou'tlet of the" Among the organic absorbents which;may be used other than acetone are acetaldehyde, ace-'- tonitrile,nitrobenzene, chlorinated hydrocarbons, poly-vv gaseous eilluent.

gaseous in nature and comprise essentially, diacetylene, v

methyl acetylene, and vinyl acetylene. The gaseous cycled for acetylenerecoveryto a second acetylene-absorbing zone in the usual manner. Theacetone bottoms from the tower 10l contain approximately l0 percent ofthe acetylene and substantially all of the acetyleneA homologues andpolymers contained in the reaction gases entering the tower throughtheline 12'from the compressor.A

Adjacent the lower end portion of the absorbing towery 10 is a liquidlevel control valve 18 which reduces the pressure of the outgoing'acetone stream to arpressure which is suicient to force the processliquid into a lirst stripping tower 20. The acetone bottoms emergingfrom the absorbing column 10 are passed into the packed stripping column20 by means of a line.22. The down# v tars.

wardly flowing acetone stream which contains the acetylene homologuesand polymers, countercurrently contacts an upwardly ilowing stream ofstripping gas which enters the .column 20 through line 24. The strippinggas is inerteto both the acetone and the gases dissolved therein and, inthe course of its upward movement through the tower strips olf theacetylene present in the acetone bottoms; negligible amounts ofdiacetylene and methyl acetylene are also driven olf. This gaseousoverhead emerging from tower 20 through line 26 is recycled to thecompressor (not shown) lfrom which it once more enters contacting towerthrough line 12, whereby the acetylene values contained therein may berecovered.

The acetone bottoms containing the major proportion of the acetylenepolymers and homologues from the tower 20 are forced by a pump 25through line 28 to a Vsecond stripping .column30. However, prior toentrance into the columnV 30, the acetone is diluted with water, whichis conveyed by means of valved line 32. The acetone should be diluted tothe extent that the normally gaseous acetylene homologues and polymersare no longer soluble in the acetone and are, therefore, enabled to bedriven off as gases in the overhead gaseous discharge through line 33.Diluting the acetone bottoms to effect about a l5-50% acetone solutionis generally suiicient to insure substantially complete removal of thegaseous acetylene polymers and homologues. This stripping.y action iseffected by means of a suitable gas entering the column 30 through line34. The volume of stripping gas utilized in bothy columns 20 and 30` isapproximately 25 to 50 standard cubic feet for each gallon of absorbentsolution.

It should at this timebe noted that the removal of the acetylenepolymers and homologues as gases is an important feature vof theprovided process. By priorV art For a more complete understanding,reference will now be made to the following example illustrating themanner of carrying out this invention.

About 5,000 standard cubic feet per hour of reaction gases equivalent toapproximately 700 standard cubic feet per hour of acetylene (bothcalculated at normal atmosphericpressure and temperature) are passedinto the bottom of the absorbing column 10 at about 200 p.s.i.g. incountercurrent contacting flow relationship with from 6 to 10 gallonsper hour of acetone entering the top of the tower. The acetone bottomscontaining approximately 10 percent acetylene and substantially all ofthe acetylene polymers and homologues are passed through the liquidlevel controlled pressure-reducing valve 18 into the first strippingtower 20 in countercurrent contacting flow with 27.5 cubic feet ofstripping gas for every gallon of acetone. The tower 20 is maintained at-about 5 p.s.i.g. The acetone bottoms from the rst stripmethods theabsorbent for acetylene, its homologues and polymers, was processed sothat the homologues and polymers precipitated `out as hard-to-removegums and In accordance with the present process, however, theundesirable homologues and polymers are readily driven oi as gases,leaving the remaining absorbing fluid free of dilcult-to-removetars andgums, thereby obviating additional processing steps and the expensethereof.

The bottoms from stripping tower 30 are thus seen to contain acetone andwater which are removed from the tower by means of pump 35 and thencethrough line 36. The acetone-water mixture then passes into distillationcolumn 38 heated by steam coils 39 wherein the acetone is drivenoverhead through line 40, liquefied in condenser 42, and then passedinto a receiving vessel 44 from which it may be recycled to the mainacetone system by means of a pump 46.

As a modification of the above process, a portion of the acetone streamfrom the main acetylene absorption system (not shown) essentially freeof acetylene and containing some homologues or polymers such as methylacetylene may enter the line 28 by means of a valved line 48, as theacetone bottoms ofstrippingcolumn 20 are in the process of being passedinto the stripping column 30. It will be appreciated that the homologuesand polymers will also be removed from this stream in the tower 30.

An additional modification of the above process, which may be utilizedin combination with the above modifcation, is the provision of a lterinterposed in the line 36 between strippingcolumn 30 and thedistillationl column 38. Although the acetylene polymers and homologuescontained in the acetone or other organicabsorbent are normally gaseous,some high molecular weight polymers may precipitate out as solids 'upondiluting the organic absorbent with water. Consequently, to remove thesesolids the interposing of a 'lter 50 `be tween column 30 anddistillation column 38 facilitates the vfinal processingsteps of .theacetone-water mixture.

recycling and reuse.

ping tower contain approximately 2.9 percent by weight acetylenehomologues, calculated as acetylene, which are then diluted with waterto give an acetone content of 20 percent by weight in tower 30. Thisdiluted acetone V`stream containing the acetylene homologues andpolymers is also stripped with 27.5 cubic feet of stripping gas forevery gallon of acetone in a second stripping tower. The resultingacetone bottoms emerging from the second stripping column 30 aredistilled; the resulting acetone distillate contains 0.02 percentacetylenes by weight.

It is thus seen that an improved process for the regeneration of anorganic absorbent containing acetylene, its homologues and polymers, hasbeen provided which is readily adaptable to large scale, commercialoperations. The undesirable polymers and homologues of acetylene, whichheretofore had been removed only as gums or tars are now removed, inaccordance with the provided process, as a gas leaving and remainingacetone absorbing liquid or other organic absorbent in a ready state forIn addition, no additional chemicals are needed to bring the homologuesand polymers out of solution with the absorbing liquid. The providedprocess effects the separation by the mere use of water which dilutesthe absorbing liquid and thus causes the dissolved homologues andpolymers to assume their normal gaseous state. The stripping gases usedin towers 20 and 30 may be air, nitrogen, methane, natural gas or, aspreviously suggested, any gas that is inert to the absorbing liquid andthe acetylenic compounds.

While several particular embodiments of this invention are shown above,it will be understood, of course, that the invention is not to belimited thereto, since many modifications may be made, and it iscontemplated, therefore, by the appendedclaims, to cover any suchmodiiications as fall within the true spirit and scope of thisinvention,

We claim:

1. A process for removing acetylene homologues and polymers from anorganic absorbing liquid containing acetylene homologues and polymersdissolved therein comprising the steps of reducing the solubility ofacetylene homologues and polymers in the absorbing liquid by dilutingthe absorbing liquid with water until said acetylene homologues andpolymers are no longer soluble therein, stripping the acetylenehomologues and polymers from said absorbing liquid by passing an inertgas therethrough,

and separating the water from the absorbing liquid.

2. The process as recited in claim l in which the organic absorbingliquid is acetone.

3. A process for removing acetylene homologues and polymers from anorganic absorbing liquid comprising the steps of reducing the solubilityof acetylene homologues and polymers in the organic absorbing liquid bydiluting the organic absorbing liquid with Water until said acetylenehomologues and polymers are no longer soluble therein, removing anynormally solid acetylene homologues and polymers from said organicabsorbing liquid by filtration, removing the normally gaseous acetylenepolymers and homologues from said organic absorbing liquid by passingsaid liquid in countercurrent contacting flow ywith an inert strippinggas, and removing the Water from the resulting diluted organic absorbingliquid.

4. A process for removing acetylene and acetylene homologues fromacetone which comp-rises passing under superatmospheric pressure acetonehaving acetylene and its homologues dissolved therein into a iirststripping zone of lesser superatrnospheric pressure in countercurrentcontacting ow with a rst quantity of stripping gas,` cycling theoverhead acetylene enriched stripping gas to an acetylene recoverystation, mixing the acetone bottoms with water, passing the acetonebottoms-Water mixture into a second stripping zone in countercurrentcontacting flow with a second quantity of stripping gas, passing theresulting gases overhead, and separating said resulting acetone-waterbottoms into water and acetone by fractional distillation.

5. A process for regenerating an organic absorbing liquid havingacetylene homologues and acetylene polymers dissolved therein whichcomprises passing an organic absorbing liquid containing normallygaseous acetylene polymers and homologues into a rst stripping zone incountercurrent contacting flow with a lirst quantity of stripping gas,cycling the gaseous overhead for recovery, diluting the organicabsorbing liquid with water until the normally gaseous acetylenepolymers and homologues are no longer soluble therein, passing thediluted organic absorbing liquid into a second stripping zone incountercurrent contacting flow with a second quantity of stripping gaswhereby said normally gaseous acetylene polymers and homologues aredriven oi in the gaseous overhead, and fractionally distilling theresulting bottoms to separate the organic absorbing liquid from thewater mixed therewith.

6. The process as recited in claim 5 in which said organic absorbingliquid is acetone.

7. A process for regenerating acetone containing acetylene and itshomologues which comprises passing under pressure acetone containingacetylene and its homologues into a iirst stripping zone of lesserpressure in countercurrent contacting flow with a rst quantity ofstripping gas, cycling the overhead acetylene-enriched stripping gas forfurther processing, mixing the acetone bottoms with water, passing theacetone bottoms-water mixture into a second stripping zone incountercurrent contacting ow with a second quantity of stripping gas,Washing the resulting gaseous overhead and passing it to the atmosphere,filtering the resulting acetone-water bottoms, and separating saidresulting acetone-water bottoms into water and acetone by fractionaldistillation.

8. A process for regenerating acetone containing acetylene and itshomologues which comprises passing under pressure acetone containingacetylene and its homologues into a rst stripping zone of lesserpressure in countercurrent contacting flow with a rst quantity ofstripping gas, cycling the overhead acetylene-enriched stripping gas forfurther processing, adding substantially acetylene-free acetone to saidbottoms whereby acetylene homologues contained therein may be removedthereby, mixing the acetone bottoms with water, passing the acetonebottomswater mixture into a second stripping zone in countercurrentcontacting llow with a second quantity of stripping gas, passing theresulting gases overhead, filtering the resulting acetone-water bottoms,and separating said resulting acetone-water bottoms into water andacetone by fractional distillation.

9. A process for removing acetylene homologues and acetylene polymersfrom an organic absorbing liquid which comprises passing an absorbingliquid containing acetylene, acetylene polymers and homologues into arst stripping zone in countercurrent contacting flow with a trstquantity of stripping gas, cycling `the gaseous overhead for recovery ofthe acetylene values contained therein, diluting theV organic absorbingliquid bottoms with Water until the normally gaseous polymers andhomologues and the normally-solid high molecular weight polymers are nolonger soluble in the organic absorbing liquid bottoms, filtering thebottoms whereby the normally solid polymers are removed from theabsorbing liquid, passing the bottoms into a second stripping zone incountercurrent contacting ilow with a second quantity of stripping gaswhereby said normally gaseous polymers and homologues are driven off inthe gaseous overhead, and fractionally distilling the resulting bottomswhereby the organic absorbing liquid is separated from the water ofdilution mixed therewith.

l0. The process -as recited in claim 9 in which said absorbing liquid isacetone.

ll. A process for regenerating acetone containing acetylene andacetylene homologues which comprises passing acetone containingacetylene and its homologues into a firststripping zone incountercurrent contacting flow with a first quantity of stripping gas,cycling the gaseous overhead for further processing, mixing the acetonebottoms containing acetylene homologues with water, passing thebottoms-water mixture into a second stripping zone in countercurrentcontacting flow with a second quantity of stripping gas, passing thegaseous overhead from said second stripping zone to the atmosphere, andseparating the resulting acetone-water bottoms into its acetone andwater constituents. v

l2. A Aprocess for regenerating an organic absorbing liquid containingacetylene and acetylene homologues which comprises passing saidorganic-absorbing liquid containing acetylene and its homologues into arst stripping zone in countercurrent contacting ow with a rst quantityof stripping gas, cycling the gaseous overhead for further processing,mixing the organic-absorbing liquid bottoms containing acetylenehomologues with water, passing the bottoms-water mixture into a secondstripping zone in countercurrent contacting ow with a second quantity ofstripping gas, passing the gaseous overhead from said second strippingzone to the atmosphere, and separating the resulting bottoms from saidsecond stripping zone into its organic absorbing liquid and waterconstituents.

References Cited in the le of this patent UNITED STATES PATENTS1,422,182 Curme July 11, 1922 2,250,925 Babcock July 29, 1941 2,715,947Alexander Aug. 23, 1955 2,738,859 v Bartholome et al Mar. 20, 19562,738,860 Lorenz et al. Mar. 20, 1956 2,838,133 Schreiner June 10, 1958

1. A PROCESS FOR REMOVING ACETYLENE HOMOLOGUES AND POLUMERS FROM ANORGANIC ABSORBING LIQUID CONTAINING ACCETYLENE HOMOLOGUES AND POLYMERSDISSOLVED THERIN COMPRISING THE STEPS OF REDUCING THE SOLUBILITY OFACETYLENE HOMOLOGUE AND POLYMERS IN THE ABSORBING LIQUID BY DILUTING THEABSORBING LIQUID WITH WATER UNTIL SAID ACETYLENE HOMOLOGUES AND POLYMERSARE NO LONGER SOULABLE THEREIN STRIPPING THE ACETYLENE HOMOLOGUE AND THEPOLYMERS FROM SAID ABSORBING LIQUID BY PASSING AN INERT GASTHERETHROUGH, AND SEPARATING THE WATER FROM THE ABSORBING LIQUID.